Raise Python floor to 3.11 and bump backend extras

[Superagentic-AI]

Summary

Raises the supported Python floor from 3.10 → 3.11 and bumps optional quantum-backend extras to current majors verified on PyPI (2026-09-04). This is a breaking change for Python 3.10 users: installers on 3.10 will no longer resolve superquantx.

Several backends (PennyLane 0.45, Cirq 1.7, Amazon Braket SDK 1.127) already require Python ≥3.11, so keeping a 3.10 floor was no longer coherent with the extras we advertise.

Python floor

• requires-python = ">=3.11"
• Classifiers / ruff / black / mypy targets updated (3.9/3.10 removed)
• README, install/quickstart docs, and contributing/dev docs no longer advertise 3.10
• Core scientific floors left 3.11-compatible (do not force NumPy/SciPy majors that require Python ≥3.12)

Backend extra floor bumps (verified on PyPI)

Extra	New declared floor	Latest verified
pennylane	pennylane>=0.45.0, pennylane-lightning>=0.45.0	0.45.1 / 0.45.0
qiskit	qiskit>=2.0,<3, qiskit-aer>=0.17.0, qiskit-ibm-runtime>=0.49.0	2.5.2 / 0.17.2 / 0.49.0
cirq	cirq>=1.7.0	1.7.0
braket	amazon-braket-sdk>=1.127.0	1.127.0
tket	pytket>=2.18.0, pytket-qiskit>=0.78.0	2.18.1 / 0.78.0
ocean	dwave-ocean-sdk>=9.0.0, dimod>=0.12.22	9.4.0 / 0.12.22

Qiskit 2.x policy

Qiskit extras now use an explicit 2.x range (qiskit>=2.0,<3) instead of open-ended >=1.0. The Qiskit wrapper was audited and minimally fixed for APIs removed or changed under 2.x:

• qiskit.execute → backend.run / Statevector
• bind_parameters → assign_parameters
• Aer.get_backend fallback → AerSimulator
• classical-register name clash when measuring circuits created by create_circuit

Compatibility table

Added a declared/tested backend version table in docs/BACKENDS.md.

CI workflow note (follow-up needed)

Updating .github/workflows/ci.yml (drop 3.10 from the test matrix; optionally add 3.13) failed to push because the authenticated OAuth app lacks the GitHub workflow scope. Please apply that matrix change in a follow-up with a token that has workflow scope. docs.yml already uses 3.11 and was left unchanged.

Test results / gaps

• Core unit tests (pytest tests/unit/ --no-cov): 73 passed, 14 failed, 2 skipped.
• Failures look pre-existing / environment-related, not introduced by the floor bump:
  • Braket/Ocean tests: mock/NetworkX assertion issues with backends not fully wired in unit mocks
  • Circuit __repr__ / pydantic positional-arg expectations
  • Async client tests needing pytest-asyncio plugin wiring
• All optional extras installed successfully at the new floors (pennylane, qiskit, cirq, braket, tket, ocean).
• Qiskit 2.5.2 smoke test: get_statevector + execute_circuit OK after wrapper fixes.
• Full integration / hardware suites not run.

Package version in src/superquantx/version.py was not bumped (release process unchanged).

Test plan

• Confirm pip install / uv sync rejects Python 3.10 and succeeds on 3.11+
• uv sync --extra qiskit resolves qiskit>=2,<3 and runs a small circuit
• Spot-check other extras install on 3.11
• Follow-up PR: CI matrix ["3.11", "3.12", "3.13"] once workflow scope is available
• Optionally triage the 14 pre-existing unit failures separately

[Superagentic-AI]

Follow-up: CI Python matrix

This PR raises requires-python to >=3.11, but .github/workflows/ci.yml still has:

python-version: ["3.10", "3.11", "3.12"]

Pushing that one-line change needs a token with the workflow scope (the shared gh OAuth login and the GitHub plugin both lack it). Please either:

1. Edit ci.yml on this branch in the GitHub UI to ["3.11", "3.12"], or
2. Push that change from an account/token that can update workflow files.

Everything else in the PR is already on the branch.